Examples:1. - Your boat moves to the current tile in a direction complete opposite to the current direction (arrow), and your speed is 7 and the 4th step is on the current tile:Then after the 4th step your boat moves 1 step back (current direction), then the 5th step again on the current tile, then 1 step back again, then 6th step on the current tile again, 1 step back again and 7th step forward and back again. So you cannot pass the current in opposite direction. This may seem hard, but sometimes this makes that you can make more speed and use the current as a kind of soft cushion before turning in an other direction next move.Other directions to enter the current give other problems/possibilities.